Install telnet with Homebrew

Project links

• Homepage
• Repository

Commands and aliases

• telnet

Project history

The BSD-derived Apple manpage carries University of California copyright dates beginning in 1983 and describes `telnet` as a user interface to the TELNET protocol. This places the packaged client in the long Unix lineage of TCP/IP remote-login tools distributed with BSD systems and later carried by operating-system vendors.

RFC 854 defines the protocol around a Network Virtual Terminal and negotiated options, with the goal of connecting terminal devices and terminal-oriented processes across heterogeneous hosts. The companion RFC 855 documents how TELNET options were to be assigned and specified.

Adoption history

TELNET was once a standard remote-login mechanism on Internet and Unix systems, but its cleartext nature caused SSH to replace it for administration. The client persisted in package repositories because it remained useful for protocol debugging, legacy devices, embedded systems, MUDs, BBS-style services, and quick TCP service inspection.

Homebrew's package exists because modern macOS no longer treats telnet as a default userland tool, while Debian, Ubuntu, Fedora/DNF, openSUSE/Zypper, Chocolatey, and Scoop coverage reflects ongoing cross-platform demand for the small diagnostic client.

How it is used

The manpage describes invoking `telnet` with a host and optional port, or without a host to enter an interactive `telnet>` command mode. Options cover IPv4/IPv6 selection, trace files, source address selection, escape characters, `.telnetrc` handling, rlogin-like behavior, Kerberos-related authentication controls, binary mode, and optional encryption support where compiled in.

In package-manager culture, `telnet host port` became shorthand for testing whether a TCP service accepts connections, even when the remote service is not a TELNET server. That usage survives because the client is tiny, scriptable enough for manual diagnostics, and familiar across Unix-like systems.

Why package nerds care

telnet is historically significant because it is both a protocol tool and a fossil of early Internet userland. Package nerds care about it as a removed-default utility that keeps reappearing in bootstrap scripts, debugging recipes, and compatibility packages despite being inappropriate for secure login.

Its package metadata also illustrates how old network clients move from base operating systems into optional package-manager formulae as security expectations and default installs change.

Timeline

• 1983: RFC 854 standardized TELNET for the ARPA Internet.
• 1983: RFC 855 standardized TELNET option specification procedures.
• 1983-1994: BSD telnet manpage lineage records University of California copyrights and Berkeley manual revisions.
• 2000: Apple-distributed telnet manpage date reflects later operating-system packaging of the BSD-derived client.

Related projects

• telnetd is the companion server for the same protocol.
• ssh replaced TELNET for secure remote login, while tools such as nc, socat, curl, and openssl s_client cover many modern diagnostic use cases.

Sources

• https://github.com/apple-oss-distributions/remote_cmds/blob/main/telnet/telnet.1
• https://www.rfc-editor.org/rfc/rfc854.txt
• https://www.rfc-editor.org/rfc/rfc855.txt
• source_facts.package-manager